3582287379

1.    (2) Tnie or false? Uydrogen bonding is what causes icc to be less dense than liquid water.

2.    (2) Tnie or false? Water has a high diclectric conslant bccausc it has a dipole moment.

3.    (3) A buffered solution (choosc all answers that apply):

a.    Has a pH elose to 7.

b.    Rcsists changcs in pil.

c.    Contains an acid and a base.

d.    1 las a zero avcragc charge, c. I las a pKa elose to 7.

4.    (7) Givcn the following dipeptide:

H,

h_2sj

/ \ h₄ h₅

II

c₂

o₂

nr v^H»

o₃-

\

c / ^

/ ⁿh₉

H,o

H

u

a.    List all atoms contained within one peptide piane.

b. List the four atoms whosc positions arc uscd to mcasurc the if dihedral anglc.

c. List the four atoms whosc positions arc uscd to mcasurc the y dihedral anglc.

5.    (7) The strueture of D-erylhrose is shown to the right:

s LI	_/\u
H —	OH
H — c	—OH :h2oh

a.    Considcring aldoscs and ketoses, how many different (linear) tetroses are therc? Bricfly show your rcasoning

b.    Which carbon of a tetrose determines if it is D or L?

(Give the carbon's number.)

c.    Draw a Haworth projcction of one anomer of D-crythrofuranosc and circlc the anomerie carbon.

6.    (4) You sce a news report describing the discovcry of a ncw polysaccharide in fungi. The report says the polysaccharide is composcd only of rcpcating, linkcd sucrosc units. but givcs no further details of the polysaccharide strueture. Why is it likcly that cithcr the report is inaccuratc or the discovcry is false? (Explain in 40 words or fewer.) /fint: Consider the linkages in polysaccharides.

Page 2 of7